The present invention generally relates to a copying apparatus and more particularly, to a copying apparatus equipped with an original document circulation feeding arrangement adapted to feed a plurality of original document sheets placed or stacked on an original document tray, through circulation one sheet by one sheet, onto an original document platform.
Commonly, an automatic document feeder (referred to as an ADF) to be mounted on a copying apparatus includes an original document tray, an original document transport means and an original document discharge tray, and is arranged to lead a plurality of original document sheets placed on the original document tray to an original document platform, one sheet by one sheet, through the original document transport means, and to discharge said original document sheets onto the discharge tray after completion of predetermined functions. Meanwhile, a conventional original document circulation feeding apparatus is so arranged as to transport the original document sheet onto the original document platform, from the sheet located at the lowermost position of such original document sheets stacked on the original document tray, and to discharge the original document sheet on the original document platform onto the uppermost position of the original document sheets stacked on the original document tray after completion of the predetermined functions. By the above action, in the original document circulation feeding apparatus, the order of the original documents piled up on the original document tray is not altered even after termination of feeding function for all of the original document sheets. Generally, the conventional automatic document feeder including the original document circulation feeding apparatus is provided with a detecting means for detecting sizes of original document sheets for the purpose of effectively utilizing the function related to copy paper selection of the copying apparatus on which such automatic document feeder is to be mounted. In most of the known automatic document feeders, the detecting means as referred to above is provided in the vicinity of the original document tray so as to effect the detection of sizes of the original document sheets on the original document tray. Therefore, in the case where original document sheets in a plurality of various sheet sizes are simultaneously placed on the original document tray, only the maximum size of such paper sizes is detected, and the functions of the copying apparatus can not be fully utilized for the original documents having sizes smaller than that. Although there was also conventionally proposed an automatic document feeder having a detecting means arranged to detect sheet sizes during feeding of the original document sheets from the original document tray, such a detecting means was exclusively used for the classification of the original document sheets afer discharging thereof, since it is difficult to effect alteration of paper sheets, etc. after feeding of the original document sheets from the viewpoint of timing.
Accordingly, in any of the copying apparatuses provided with the prior art automatic document feeders, there has been such a disadvantage that it is impossible to continuously feed the original document sheets in a plurality of various sizes, to the original document platform, thereby to effect the copying operation based on copy paper sheets and data suitable for the original document sheets of the respective sheet sizes.